1. Field of the Invention
The present invention relates to metal injection-molding (MIM) and in particular relates to an injection-moldable metal powder-binder feedstock and to a method of forming a metal injection-molded article. Metal injection-molding involves mixing one or more metal or alloy powders with a fugitive binder to form a homogeneous injection-moldable feedstock, which is then injection-molded to form a shaped body which is commonly referred to as a "green body". The binder is then removed from the green body and the body is then sintered to fuse the metal powder to a solid which retains the original injection-molded shape.
2. Description of the Related Art
Various binders are known in the prior art and typically consist of plain paraffin wax or carnauba wax and one or more polymers. The wax components act as a lubricant during injection-molding and have conventionally been removed by placing the injection-molded green body on a bed of finely divided alumina-ceramic powder and melting the wax binder. The molten wax is sucked out of the green body into the alumina powder bed by capillary action. However, such a process tends to roughen the surface of the product and the cost of the required grade of alumina powder represents a significant expense.
Other techniques used in the prior art include the use of various solvents to remove the binder but such techniques lead to additional complications and disadvantages.